Abstract 2626: Adenosine Induced Vasodilation Enhances the Assessment of Microvascular Obstruction and Hypoperfusion Following Reperfused Myocardial Infarction Measured by Computed Tomography
Background: We have previously validated the accuracy of infarct size and microvascular obstruction (MVO) assessment following myocardial infarction (MI) using delayed enhanced multidetector computed tomography (DE-MDCT). Additionally, we have shown that myocardial perfusion deficits on first-pass helical MDCT imaging (FP-MDCT) during adenosine infusion represent areas of decreased perfusion in the setting of coronary stenoses. This study aims to compare the extent of hypoperfused myocardium by FP-MDCT during adenosine infusion with MVO by DE-MDCT.
Methods and Results: Six porcine models of anterior myocardial infarction underwent FP-MDCT imaging five minutes into adenosine infusion (0.14 mg/kg/min) 10 days following reperfusion. Using bolus tracking, the scan was initiated when a threshold of 150 Hounsfield units was detected in the left ventricular blood pool during a 2.5 ml/sec contrast infusion for a total contrast dose of 45 ml. Following FP-MDCT, additional contrast was infused for a total of 150 ml. Ten minutes following contrast infusion, DE-MDCT was performed. The imaging protocols were as follows: detector collimation: 0.5 mm X 64, 120 kV, 400 mA. Images were reconstructed at a cardiac phase of 80% and analyzed using a custom perfusion software package. Density thresholds defined the infarct on DE-MDCT as one standard deviation above the remote myocardial density and the perfusion deficit on FP-MDCT as one standard deviation below the remote myocardial density. Areas of microvascular obstruction (MVO) were defined as hypoenhanced areas within the infarct. Mean infarct size and MVO on DE-MDCT was 14.8 ± 3.3 ml and 0.07 ± 0.06 ml, respectively. The perfusion deficit volume measured on FP-MDCT was 4.6 ± 2.3 ml. Compared with DE-MDCT, the area of hypoperfusion on FP-MDCT underestimates the extent of myocardial infarction, mean difference: -10.2 (p<0.001). However, the area of MVO on DE-MDCT significantly underestimates the extent of hypoperfu-sion noted on FP-MDCT, mean difference: -4.5 ml (p<0.01).
Conclusion: While DE-MDCT accurately assesses the extent of non-viable myocardium following reperfused MI, FP-MDCT more accurately delineates the extent of the hypoperfused microvasculature secondary to no-reflow.